1. Field of the Invention
The present invention relates to a defect search method for managing a defect list using a physical address and, more particularly, to a technique for searching for a defective region present in a disk upon reproduction/recording of a recording medium such as a DVD-RAM (Digital Versatile Disc-Random Access Memory) or the like.
2. Description of the Related Art
A DVD-RAM suffers defects and scratches formed in the manufacture, and defects formed by deterioration due to repetitive use. For this reason, a defect management system for managing such defects is required. By adopting a defect management system, the reliability of recorded data can be maintained high even when a disc suffers defects.
As one of defect management systems, a scheme for assuring a defect list that describes defective addresses in a disc is known. This scheme searches for defective sectors/blocks based on the defect list. Then, a defective region is skipped, and a normal sector/block after the skipped region is used.
The defect list recorded in the disc is normally described using serial physical addresses that start from the inner periphery of the disc. On the other hand, a host-PC that issues a read/write command of the disc accesses the disc using logical addresses. The logical addresses are serial addresses which exclude defective sectors and blocks. For this reason, in order to search for defects in the disc, the defective addresses in the defect list must be converted from physical addresses into logical addresses, and the request address must then be collated with these logical addresses.
A conventional apparatus and method for searching for a defective address of a recording medium will be described below using FIG. 1. FIG. 1 is a block diagram showing a model of a conventional apparatus for searching for a defective address of a recording medium.
As shown in FIG. 1, firmware 10 has a buffer RAM 12, first converter 11, second converter 14, and comparator 13.
The first converter 11 reads out a defect list recorded in a disc 20. The first converter 11 then converts defective addresses contained in the defect list from physical addresses into logical addresses. The buffer RAM 12 stores the defect list that contains defective addresses which have been converted into logical addresses by the first converter 11. The comparator 13 compares the defect list stored in the buffer RAM 12 with a logical address requested from a host-PC 30. The second converter 14 converts the logical address obtained by the comparator 13 into a physical address to access the disc 20.
In this way, the defective addresses in the defect list recorded in the disc 20 are physical addresses, and a request address from the host-PC 30 is a logical address. For this reason, these addresses cannot be directly compared. Hence, after the defective addresses are converted from physical addresses into logical addresses, the request address is compared with the defective logical addresses.
However, this conversion process is a heavy load on the firmware 10. This is because the defective addresses are read out from the defect list, and must be skipped during reproduction/recording. For this reason, not only a reproduction/recording start address but also all subsequent addresses must be converted from logical addresses into physical addresses.
The above method suffices to manage primary defects formed in the manufacture. However, defect management must be done not only for primary defects but also for secondary defects. The secondary defects are those caused by, e.g., deterioration of a disc in use. Every time a secondary defect is generated, it is replaced by the normal block. However, once all the defective addresses in the defect list are converted into logical addresses, the secondary defect cannot be coped with. For this reason, another defect list described using physical addresses must be independently stored in the buffer RAM 12 so as to search for primary defects in the block replaced due to secondary defects. That is, the buffer RAM 12 must store two defect lists described in physical and logical addresses. As a result, a large-capacity buffer RAM 12 is required.